Indirect Cylinder Hot Water Help

sal0007

Hello all,

Long story short: My previous home had a combi boiler, but new home has a Gledhill indirect cylinder, gas boiler + Honeywell smart thermostat for the hot water setup, and I just can't get my head round how it works. I've read the manuals, researched online etc and still not too sure. Can anybody help/point me in the right direction with the questions below:

1. I've been advised that the cylinder is "just a back up", so even though I've set my hot water setting on the Honeywell Smart thermostat to "always off",  I still get hot water when I open the tap. How is this being heated - elec or gas? 
2. If I set the Smart thermostat to "always on", how does this work? 
3. From research online I can see most people tend to have a hot water schedule in place. How does this work? Presumably the boiler heats the water at these set times?

Just looking to get an efficient setup in place so appreciate any advice

Thanks!

sal0007

Also worth adding that given the cylinder "is a backup" advice, I turned off the switch next to the Cylinder. I had hot water for approx 24hrs, but after that no more hot water. (Smart thermostat set to "always off") I switched it back on and hot water returned after an hour or so.

So what is the ideal setup

molerat

The cylinder is not a back up, the electric heating of it is the back up and that was obviously turned on.  Unless you can heat it with free solar electric using your gas boiler will be the cheapest method. You now need to sort out your smart controller to provide hot water.  A lot will depend on your water needs but as it took 24 hours for you to run out of hot water likely a couple of hours a day would provide enough.  Set it to come on an hour before you get up for a couple of hours and see how it goes.  You can then modify it to suit your needs.

Alnat1

The switch on the wall is for the immersion heater in the tank and uses expensive electricity (around 23p per kWh) to heat the water. It's much cheaper to use gas (around 6p per kWh)

You need to set the Honeywell to hot water timed, assuming that is an option. Set if to come on for a couple of hours a day, probably best early morning if that's when most have showers, or late afternoon if you have evening showers.

sal0007

molerat said:

The cylinder is not a back up, the electric heating of it is the back up and that was obviously turned on.  Unless you can heat it with free solar electric using your gas boiler will be the cheapest method. You now need to sort out your smart controller to provide hot water.  A lot will depend on your water needs but as it took 24 hours for you to run out of hot water likely a couple of hours a day would provide enough.  Set it to come on an hour before you get up for a couple of hours and see how it goes.  You can then modify it to suit your needs.

Thanks, so if i've not got it set up using the smart thermostat, every time I open the tap it will be using the electric heating in the cylinder to heat the water?

If I set up a schedule on the smart thermostat, can I turn the switch off next to the cylinder? Presumably the timer will ensure that the boiler has heated the water?

molerat

Your primary method to heat the water is the gas boiler.  The switch next to the tank is the back up, you will see a wire going to a round can on the side of the tank - that will be a 3kW heater. That switch needs to be off at all times. The timer will tell the boiler to heat the water.  There will be a thermostat on the tank to turn the boiler off when fully hot but with a limited water need the timer will likely switch off before the whole tank is heated.

sal0007

Alnat1 said:

The switch on the wall is for the immersion heater in the tank and uses expensive electricity (around 23p per kWh) to heat the water. It's much cheaper to use gas (around 6p per kWh)

You need to set the Honeywell to hot water timed, assuming that is an option. Set if to come on for a couple of hours a day, probably best early morning if that's when most have showers, or late afternoon if you have evening showers.

Thank you - so turn off the switch next to the cylinder and set up the Honeywell on a timer. This will use gas to heat the water, and as long as the duration is right, should provide hot water. If the duration's not right, the hot water will run out?

molerat

If the duration's not right, the hot water will run out?

Correct, so you then adjust the timings to suit your needs.

matelodave

As you say, turn off the immersion heater and use the gas boiler to heat the hot water (leccy costs four times as much as gas)

Sort out your timings so that you get hot water when you need it and dont keep heating it when you dont.

For example if you generally ablute in the mornings then heat the tank for an hour or so so you have sufficient hot water to for showers etc. Then perhaps give it an hour or so before your bedtime bath if thats your thing. Just adjust your timing to ensure that you have enough when you need it. You dont need to keep the tank hot all night or even all day if you are out at work.

Its also a good idea to reduce your tank temp down  to around 50 degrees - a hotter tank loses more heat and you end up diluting your hot water with cold to make it usable.

Dont run the hot tap to rinse stuff (including your hands).  Everytime you run off several litres of cold to get hot water you leave the same amount to get cold in the pipes. Take shorter showers, five minutes or less and perhaps fit an eco shower head to reduce the volume of water used.

We get away with heating our tank for just an hour a day in the winter and less that, 1.5hours every two days in the summer and we have plenty of water for the two of us to have a shower each every day.

JohnSwift10

That is one advantage of a combi boiler, instant hot water and no need for timers and thermostats. 

Bendo

If by instant you mean after letting the tap run for a while and by hot, you mean lukewarm.